Title
L-828, Type L-829 Ferroresonant Constant Current Regulator (CCR) - Running a Manual Megger (IRMS) Test
URL Name
Running-a-Manual-Megger-IRMS-Test
Summary
Defines the procedure for initiating and performing a manual insulation resistance (IRMS) test using a CCR equipped with Megger capability.

Content

Overview

The Manual Megger function allows the operator to measure insulation resistance of the series lighting circuit using the CCR’s built-in IRMS system.

This test evaluates circuit integrity without disconnecting the loop.

It should only be performed when safe to apply a test voltage to the series circuit.

When to Perform a Manual Megger Test

Run a manual test when:

  • Investigating suspected ground faults

  • Insulation degradation is suspected

  • After cable or fixture repair

  • During preventative maintenance

Do not perform the test while personnel are working on the series circuit.

Preparation

Before initiating the test:

  • Ensure no personnel are working on the field circuit.

  • Verify the CCR is in a safe condition.

  • Confirm IRMS is enabled (if applicable).

  • Ensure no active fault condition prevents testing.

Procedure

  1. Power the CCR.

  2. Navigate to the IRMS or Megger function via the DCMU interface.

  3. Select Manual Test.

  4. Confirm test initiation when prompted.

  5. Allow the test to complete without interruption.

The CCR will apply a test voltage and calculate insulation resistance.

Viewing Results

After completion:

  • The measured insulation resistance value will be displayed.

  • Compare the result to acceptable thresholds for the installation.

Low resistance readings may indicate:

  • Moisture in cable

  • Damaged insulation

  • Ground fault condition

  • Isolation transformer failure

If Test Fails or Shows Low Resistance

If insulation resistance is below acceptable levels:

  • Do not ignore the condition.

  • Inspect the series circuit.

  • Check cable splices and isolation transformers.

  • Investigate recent maintenance work.

Further testing may be required to isolate the fault location.

Important Notes

  • Manual Megger testing is separate from automatic monitoring.

  • Test results should be documented for maintenance records.

  • IRMS readings may vary with environmental conditions.

Safety Reminder

⚠ The Manual Megger test applies a test voltage to the series circuit.

Ensure the circuit is clear of personnel before initiating the test.

Never assume the field circuit is safe during insulation testing.

Constant Current Regulator

Related Articles

Trending Articles